media blasting - special considerations?
 

I tried last weekend to start media blasting the coupe body to start tackling the rust to see what shape the panels are in to start the repair.

My little campbell hausfield blaster and I were no match for this task. I'd better find someone to do this for me as I'd be here for months.

There aren't any places I know of in the area (Winchester VA) that are close that would do media blasting for a full car body but there is a local powdercoating shop that I was thinking of calling and asking of they would do it. They powdercoat auto frames and other large items. I am familiar with their work on patio furniture, wheels, and other items and they do a great job.

What special considerations should I take when looking for a shop that would media blast my coupe body? And how would one expect it to be priced?

By the hour or by the job? (know this probably varies between shops)

I would suspect that a company that understands media blasting would be competent enough to not destroy the body and I know it will may come out looking more haggard than when it went in with the rust coming off and the holes appearing. I just need a good working 'canvas' to start the metal work.

The front fenders are fiberglass on my coupe.. I can't afford metal and this is how she came to me so I can handle them on my own.

Re: media blasting - special considerations?
 

Ask a shop what media & pressures they use. To strip the paint, it is best to use plastic at about 35 lbs., and then the fastest way to get the rust to disappear is to use Aluminum Oxide at about 45 lbs. Low heat build-up when AO is used at that pressure. AO is much sharper than glass or sand and thus can be finer in grit to do the same job. DO NOT ASSUME just because they do media blasting that they will be competent in your sheetmetal. Have a talk so both of you understand what is expected.

BTW, in our area it generally runs about $125 an hour and to thoroughly do a Coupe body, doors, deck lid, tank, W/S frame and all of the floor pans (removed) and the body on a rotisserie takes about 6-8 hours.

.

Re: media blasting - special considerations?
 

When you think about it money wise its a deal. Ive been sandblasting bits and pieces with my little compressor about 3 years now and I'm still not Done.

Re: media blasting - special considerations?
 

Around Va.Beach there are a number of Soda Blast outfits. Some are mobile,they do alot of paint removel from boat bottoms. There also set up at Hershey in the back of the orange field. Theres another outfit in Richmond,hes allways at Field Day of the Past (sept 17-19) 3 years ago he wanted 800.00 to do a Tudor body (no fenders,hood) in my yard.

Re: media blasting - special considerations?
 

I'd certainly have to take the body someplace and not have any of the work done in my yard. I live in a 'blue blood' neighborhood with ex professional football players, Public Utility VPs, and other 'think-they're-better-than-you' people with 'sticks up their you-know-where' so any blasting won't happen around here. I get all my work done behind closed shop doors. :D

Having the knowledge of an estimated time frame (6-8) hours and a ballpark idea of per hour ($125) tells me my wallet isn't ready for this part of the restore yet. I'll have to wait a while.

Thanks to all for helping with their estimates and suggestions.

Re: media blasting - special considerations?
 

Higher pressures and you run the risk of ruining the sheet metal. Took me 15 -20 hours to sand blast mine, a coupe. I recycled the sand. Would have preferred to have it media blasted, but never had the coin. If the panels get hardened you've ruined them. Bob

Re: media blasting - special considerations?
 

The size of the nozzle is also important. I use a small nozzle 3/32", however it enlarges to about 1/8" before I replace it. A large nozzle risks damaging the sheetmetal.

Re: media blasting - special considerations?
 

Question for Bob - How can you tell if the panels have been hardened or become hardened during sand blasting??? Thanks, Harold

Re: media blasting - special considerations?
 

I wasn't impressed with the media I was using and I was probably using too high a pressure. I was using the 'Black Diamond" grit I got from Tractor Supply. The wrong stuff to use for this I'm finding out.

The blaster I was using was a birthday gift. It's probably barely adequate but I won't tell my darling wife to got it for me.

http://www.amazon.com/Campbell-Hausf...3298108&sr=8-2

I tried it out on the cowl panels that I need to replace to get my feet wet with the process to see how long it would take and the results I would get.

I'd probably have better results with a different media and the right pressures.

I'll have to keep reading and understanding the process and if I get better results with my testing I will probably end up doing it here in the shop if I can get the right technique and results.

I'd want to make a 'bay' inside the shop as well to help hold some of the media and cover up everything else. It will go everywhere but I'll try to contain some of it.

I may regret doing this myself but I'lll give it a shot.

Re: media blasting - special considerations?
 

I'm assuming(asking actually) that sandblasting wheels carries much less risk of 'ruining' the metal(?). Seems like there's not much that could go wrong(other than going slow and wasting material).

Re: media blasting - special considerations?
 

I don't think there is any risk sandblasting rims at almost any pressure. The metal is about 12 ga thick and the spokes are heavy gauge also. I have found that sandblasting 19 ga sheetmetal, which most model A sheetmetal is made of, is not to prone to warping if done by homeowner type equipment. It is the big commercial equipment with high pressure and large nozzles that can really damage sheetmetal. I suppose smaller equipment could warp sheetmetal if the pressure was set very high and the nozzle very large, but most compressors for home usage wont run long with high pressure and a large nozzle.

Re: media blasting - special considerations?
 

I have been warned not to blast one small area down completely before moving on since it may be either buckled, cause waves in the panel. When i did my coupe I would make several passes. Also, I was warned that too much pressure, and time in a small area would make it difficult to later take out small defects(do body work) since the metal would become embrittled. I had a small compressor so I did most of my work after the pressure built up. I also bled off condensation frequently. I used sand. about three passes and it became powder. I followed each session with metal prep/rust converter that I sprayed on, then wiped off with a clean rag. Bob

Re: media blasting - special considerations?
 

Banjoman. Do it outside, or behind a fence. I laid out 6mil plastic, then a tarp. I held it down with 2x4s. This caught the sand for recovery, and reuse. You don't want to fill your garage with the dust, and fine particles. Also get a hood, and a good source of fresh air to breath. The paper mask won't prevent inhaling the fines, although silicosis is a cumulative disease, and eventually if you are a smoker you won't defy the odds. This is a hot, miserable job, and worth every penny you pay to get it done by a professional. Bob

Re: media blasting - special considerations?
 

Harold, I don't know how. The body guy that refused to work on my car after I admitted I had sand blasted it was the reason I became aware that the sheet metal can become hardened by sand blasting. I understand soda blasting is less destructive. Me, I usually don't listen and learn the hard way. Bob

Re: media blasting - special considerations?
 

If I had a fence to go behind I'd do it. I have a hood and use a paint quality respirator. I know of the dangers of the dust and how much of a mess it makes.

I'll wait until air temps are in the 50s or below to tackle this. I have so much to do on this that I can keep going with the other aspects of the car till the temp makes it easier. I'll still see what prices I can get and will still do my rims and other small parts to see what works best.

I'm glad for the input I'm receiving here.

Re: media blasting - special considerations?
 

No matter what blaster you use there are a few things you must have to have for it to work. One is a compressor big enough, say 18-20 cfm (that is 5 hp). Two is dry air, like with an oil seperator & dessicant dryer. Hose big enough, 0.5" or bigger and the shorter the better. The black diamond from Tractor supply is what we use because it is rather fine. We use the nozzle size just smaller than 1/8", about 40 psi. and back off from the panel to just remove paint, slowly. WE also use a fresh air system and ventilation similiar to a paint booth.

Now when you add up all the equipment and media. Without adding any value for you time. It's very economical to pay a qualified business to do the work. The big question is which business is qualified.

Re: media blasting - special considerations?
 

I just use a small craftsman unit for portible sandblasting and black beauty sand, works great. I have been using the same set up for about 6 or 7 years only cost about $45. Sandblasted whole car bodys 5 or 6 harley frames, tools and even the inside of my wood stove pipe lol (never herd of the phrase meda blasting though). Also have a blasting cabinet for small work. Doing my rims right now I get one done in about 15-20 minits tops. (Never sandblast inside or around your undercarage assembled.) when i was 15 I decided to sand blast the frame of my jeep dam near ruined it sand found its way into every joint and bearing in the car found its way even into the engen and down into the oil pan; its Nasty stuff. also that day i learned the lesson about sandblasting indoors it was winter so I decided to sandblast insided. Killed my grage door opener got into all my power tools, angle gringers, skill saws drill press just about everything. 6 years latter I am still findind sandblasting beads places and they are still reaking havic. Just about 2 mounths ago the draws in my craftsman tool box had started letting go. After some quick ivestigation I found that the draw slides were filled with sand blasting sand and from opening and shuting after all this time with sand in there had ruined them. That was the only time I have ever sandblasted inside.

Re: media blasting - special considerations?
 

I am a retired sandblaster.

Here is a vid I made of a cheap blaster.

http://i86.photobucket.com/albums/k1...Movie_0001.jpg

Re: media blasting - special considerations?
 

Thanks for the video. As you have shown; my biggest problem was an even flow of the sand. I had to constantly adjust the pickup tube in the sand.

Re: media blasting - special considerations?
 

The standard metal tube poked into the sand is useless.

I should make a better vid one day.

I was blasting behind my hand to stop the cam lens being peppered, so it obscured the vision.

And i should demonstrate a a bit better that the sand only pools out of bottle to a set "puddle".

When blasting, it only takes what it wants, when blast is stopped, sand stops flowing too.

Re: media blasting - special considerations?
 

Soda does a nice job of removing paint, but is quite expensive. It does very little for rust though. I glass bead wheels in a cabinet and have great results. It leaves a nice finish for powder coating. I have gotten many barrels of glass beads from a highway contractor who accidentally let them get wet in a rain storm. I've dried them on a tarp in the sun and have years of free media. Using a pressure blaster, I have a hard time removing rust and not warping the metal, especially on hoods and doors. For paint I use stripper for the large flat areas.

Re: media blasting - special considerations?
 

thanks pooch. Bob

Re: media blasting - special considerations?
 

Just like to offer my thoughts on blasting after having done vintage blasting for a few decades.

When a panel is pressed from a flat sheet of metal into a shape, the outer half of the metal is stretched and the inner half is shrunk.

Blasting causes heat, heat causes metal to rise, (notwithstanding the fact that excessive pressure will blow a panel in), but with anything but the largest industrial gear, this is not an issue.

Most car panels that are have large surfaces are convex, ie, a door skin.

As you blast the outside of a door, the metal will rise out towards you, you are stretching an already stretched panel.

There is no problem with this , if you do not sit on one spot too long, and the panel relaxes to its natural stretched-pressed state after passing.

Where the problem lies, is doing INSIDE panels, where the pressing is concave and the metal is shrunk.

The slightest blasting will stretch this shrink and make the panel in fact flattish, makes the panel stretched on both sides.

Shrunk metal that has been stretched does NOT go back.

This makes too much metal in that spot, and it is now wavy.

For an example, if you blasted an A door on the inside skin and the blaster went through the access holes, it would look like the panel was blown in from the outside.

So, be very careful of blasting any shallow concaves and especially anywhere there are ribs or reinforcements crossing inside.

The metal WILL be sucked up and around the ribs, and it will NOT relax back into shape, just as if was blown in with excessive force from the outside.

I read 1/8 nozzles and 40 PSI.

Wow, who has 20 years to do a body?

The minimum for home blasting is 1/4 inch nozzle, 90 PSI and 20 CFM compressor, unless you want to die of old age before the silicosis gets you.

Here is a bit of info on "profile", it is the metal surface of craters and protrusions caused by the type of media used.

http://www.launcestonsandblasting.co...ile/index.html

Re: media blasting - special considerations?
 

I have more time than $$ so I've started tacking blasting the pieces by myself.

I made a 4x4x6 cabinet with 2x4s and an old torn tarp. staples, and a roll of Duct Tape. The cabinet is big enough to get my pieces in and the tarp enclosure does a decent job of keeping the media from going everywhere and a piece of the tarp helps funnel the media into a 5 gal bucket at the bottom to catch everything after it is used.

A piece of plexiglass for a view window and an old work shirt stapled and duct taped to the opening I made gives me good movement with gloves taped to the ends of the shirt sleeves. I used some expanded metal shelving inside for placing the work on. I use a good respirator even though the work is inside this cabinet. I'm not using sand but the Black Diamond from Tractor Supply and it looks like it is working out fairly well.

My 'contraption' Is very UGLY but large enough to house my parts and I've got about $50 in everything including the gun. I'll eventually have to blast the body but most of it is coming apart to repair so I can just and stick them in the cabinet. Doors, front cowl, wheels, trunk lid, etc.

My 80 gal compressor, a air pressure regulator and small oil/water separator right before the gun and a bigger separator at the compressor keeps the pressure right and the moisture out.

Using the bottle method described by Pooch here is working out well but I used a large funnel instead of a bottle with the same concept. I fill the funnel and it drops the media and is sucked up by the hose. No clogging and a steady stream of media. I am reusing the media after sifting it.

Thank you Pooch for posting the video and the ideas for this.

I won't be posting photos of my blast cabinet. I'd be too ashamed to show it.

Re: media blasting - special considerations?
 

The bottle or funnel is only for portable outside blasting. Total loss system.

In a cabinet, you can use a permanent piece of mesh, and shape the lower section into an inverted V.

Have a small hole at the bottom, and use a piece of 1 1/2 inch angle, and lay the suction in this trough.

Make sure the sides of the angle are above where the sand stops pooling when you stop blasting , or it will just continue to run out when stopped.

Constant recycling of sand.

Here is my portable home made one...

http://i86.photobucket.com/albums/k1...llblasters.jpg

Here is my bought cabinet, which I chopped the bottom out and made it into a "funnel". The standard steel pickup tube was useless, it would suck up about a cupful of glass bead in spits and spurts and then stop.

http://i86.photobucket.com/albums/k1.../glasscabs.jpg

And here is one I bought for $200, but have never got around to using it.
Doors both ends, elaborate sand traps at rear to minimise sand being sucked up and through fan, foot pedal, heavy duty work table.

http://i86.photobucket.com/albums/k1...rd/bigcabs.jpg

Both cabinets work on the same principle, falling abrasive being sieved and recycled automatically.

Re: media blasting - special considerations?
 

I would remove as much paint and rust first with one of those course black stripping discs.
I buy the 10" discs from tool vendors and mount them in an air angle grinder. It's much faster and less unpleasant in my opinion.
After removing 95% with discs, you can probably finish up the edges and pits with the blaster in a couple hours.
Less damaging to the metal and less mess.

Re: media blasting - special considerations?
 

I used the Sunchaser Tools, sander with "super discs". It's messy, but not nearly as bad as blasting. You can purchase the Makita sander cheaper direct from Makita. Check 'em out.

sunchasertools.com

Re: media blasting - special considerations?
 

I've had the bodywork on hold for a while, too many things going on with family, health, and work.

I've found local powdercoating company that will blast the body for me at a reasonable rate. They do it by the hour, not the job ($75 /hr) . This sounds reasonable to me.

I have sent them a test, a mower deck I'm getting ready for spring and have been pleased with their work. I only had it blasted, not coated and it the work was good. I wanted to see what they can do before handing them the body. I know the metal for the deck was thicker, I wanted to see if I was happy with what they did before giving them the coupe body.

I've also spoken with others in the area who have had work done there (not recommendations from the company itself) and they were pleased with the work that was done for them.

Once I get the remaining screws out and the hardware off I should get them the body in March.

I'll give 'em a plug after its done and I see where i need to start patching.

Re: media blasting - special considerations?
 

I am thinking of removing the paint with stripper before taking to the blaster..
What think?

Steve

Re: media blasting - special considerations?
 

You might consider having the wheels powder coated, since it is more durable than paint and not much more than the cost of sand blasting.

Re: media blasting - special considerations?
 

There is a misconception that sandblasting causes heat which then causes distortion.


We are all familiar with doing hammer on dolly work causing metal to stretch. This is from the metal being squished out.

When you use too much pressure or too much media in the stream you can beat the surface of the metal too much. This causes the surface of the metal to stretch out. Since the surface you are blasting is being lengthened, that surface will bulge out. Now I have to temper this bulge out with the fact that some surfaces may behave differently.

Now lets compare what happens with heat. The surface where the torch is applied get warmer faster then the far side. This means the torch surface will expand towards the torch while being heated. The difference is heated metal will be shrunk once it is heated beyond the plastic state. So the distortion will be different. On the middle of a convex door it will result in the overall curve being reduced.

So now what temp do you need to cause metal to shrink do to heat? Up into the 500* region gets you to the blue color which is where steel shrinks.

What happens when you have rapidly expanding air? It causes cooling. How do you think you put out a match? You are actually moving so much air that there is not enough heat to continue combustion. So exactly where do you get enough heat to significantly heat the surface of the metal?

The distortion is caused by the material beating and expanding the metal on the surface. This causes the metal to expand and make the metal curve towards the expanded metal.

To prevent distortion you need to limit the pressure and limit the amount of sand in the air stream. I have done 4 whole cars from thin French steel to my very rusty cabriolet and never had a distortion from the blasting.
Run 40 lbs or so and use the sand control to limit the amount of sand in the stream to the point at which you just see media in the air stream. I have tried to distort metal by pointing the stream at some test metal for an extended time and it would not move.

Sorry if I step on any toes with my writing.

If anyone can prove me different I am always open to facts. I have only been able to find that heat is not the cause of distortion.

Re: media blasting - special considerations?
 

I did a fair amount of outdoor blasting on my car (frame, top and bottom floorpans, etc.) with a typical generic Chinese pressure pot and a 17 CFM compressor, and I never saw any sign of distortion.

If you are concerned, try an experiment before working on your car: Get a nice flat thin piece of sheet metal, and blast away, with the highest pressure you can generate. See how what sort of damage you are capable of doing.

Doug

Re: media blasting - special considerations?
 

The pressure blaster sold by Harbor Freight for $160.00 does an excellent job. I use a hooded sweatshirt and an old welding helmet with a plain glass. Have done a John Deere and a couple of other items. I used plain old silica sand (Not suppost to) but for the money can't be beat. Also have their cabnet blaster also less that $200.00.

Re: media blasting - special considerations?
 

"I used plain old silica sand, but for the money can't be beat." I hope you have good insurance, cause your gonna need it. I'm a blaster by trade. If your using sand your asking for health issues. You may be fine for years but one day it will catch up to you. Most blasters now use fine crushed glass for metal if their any good. Keep the tip moving and back at least 8 inches from the surface. If you have any pits in your metal use a good fill and sand primer.

Re: media blasting - special considerations?
 

I purposely used the term 'media' blasting in this thread because of the fact that the word 'sand' brings up lots of discussion. I've read enough on the Internet to know that even if 50% of what i've learned is true then I want no parts of sand in any way. Sand is for beaches and the lousy soil I found when I lived in Florida.

I have a cabinet, home made that I use for small stuff and even though it is contained I still wear a respirator when using it. I've only used the 'black beauty' media I bought from tractor supply and at about 40lbs pressure. It does a fair job but the body was just too big to work with. I can't do it outside because of my HOA and the bluebloods who would try and make my life miserable for wanting to and attempt it outside.

I have been searching for a reputable place that would do something this big and not destroy my parts. I found some places quite proud of their name, their work, and their prices and wanted to charge me way more than I could afford to do it so I continued to search for a place that would be more reasonable. I felt that there was such a place out there if I kept looking.

Once I found the place I gave them a test piece to do so I could judge their work, the time it would take to get it done and was pleased with what I got back. I never mentioned the body when I took them the mower deck to blast. After I got it back and looked it over I then asked about doing the Coupe. They looked at the pictures and said that they could do it by the hour and said they believed they could do it in about 4-8 hours. My front fenders are fiberglass so they will get the rear fenders, trunk, the body and minus the cowl and the hood. That is if I can finish getting the blasted screws out..

Re: media blasting - special considerations?
 

Go to Northern Tools and buy one of their small 50lb sand blasting outfits. These have
a small red hopper which you've probably seen around. Buy the 100lb bags of fine
silicon sand. Find an area where you can make a mess. Definitely slop on the strongest paint stripper you can find, and don't hesitate to waste a few bucks
going through a few gallons of the stuff. Take the panels down until they are just
gooey primer then hose all of this chemical crap off and let things dry. Start
your blasting, but don't get so close to the metal you warp it, just spray from a distance that gets the surface rust off the back sides of your panels. Don't
blast the good side, you can just sand these by hand or DA.
Hopefully you have or will invest in a good compressor. You need this more than
anything else when it comes to restoration.

B.G.

Re: media blasting - special considerations?
 

I have personally used tons of sand for blasting Threw the years. But like every thing you need some common sense. proper protection. silicon is the second most abundant element after oxygen making up 27.7 percent of the earths crust by mass. information from wikipedia. One of my first jobs was for a commercial sandblasting and painting co.

Re: media blasting - special considerations?
 

Keep the blasting media dry! After purchasing your blasting media put into a 5 gallon paint container that has a lid with a good seal and a screw top lid. Keep it sealed up when you are not using it. Put the pick up tube of blaster gun in the screw top lid hole. Found that after doing this got better results. For Frame and a lot of other parts took to a professional who first steam cleaned the frame and parts then did the sand blasting, priming and painting. Was not cheap but got good results and have no rust anywhere.

Re: media blasting - special considerations?
 

I got the body back this morning from the blaster. They did a very good job and the cost was reasonable. I have a lot more patching than I thought. There was some previous patching done that was unknown and covered in filler.

The rear fenders are in really rough shape. I'll have to get photos posted of them. They are certainly above my skill level to repair.

Frederic County Customs in Winchester did the work. They are a powder coating shop so I had them do my wheels while they had the body.They powder coated my 16" wheels 'Fire Engine Red".

Father-in-law doesn't say much these days but its clear RED is his favourite color and the smile that came up when i showed them to him tells me he approves and we got the wheel color right.

Re: media blasting - special considerations?
 

Doug, I hate to contradict you, But when I was working on the Essex, the boss sent the fenders out for S.B.ing and the came back twisted like kandy kanes or barber poles. These were 1920 Essex, not model A, definitley a rare bird. I can't say what the media or pressures were, but they were very distorted.
Terry